The present invention relates to nuclear magnetic resonance (NMR) methods for imaging flowing fluids and stationary tissue in a sample and, more particularly, to a novel NMR method in which a response, generated for each of a set of excitations of a sample, provides medically-significant images of both fluid flow and stationary tissue in the same anatomical region.
It is known to provide NMR angiographic projection images, indicating the flow of bodily fluids through various bodily passages, for medical diagnostic purposes. Methods for producing such images are described and claimed in U.S. Pat. No. 4,714,081, issued Dec. 22, 1987, assigned to the assignee of the present application and incorporated here in its entirety by reference. While those methods provide true projection images (through the entire anatomical thickness) and allow high quality NMR angiograms of arterial and venational structures to be obtained along one or more selected projection axes and with a selected direction of flow sensitivity in a sample, it is still highly desirable to obtain the same information along with information delineating stationary tissue. This is especially important in human diagnostic imaging, where there is a clear need to replace contrast injection X-ray angiographic techniques with non-invasive NMR angiography techniques. NMR techniques are at a disadvantage with respect to X-ray methods due to the inherently low signal-to-noise ratio of NMR. Fortunately, this problem can be offset by the ability to acquire data in any dimensional volume and to acquire data from both flowing fluid and stationary tissue simultaneously, to overcome the major limitations of prior NMR and X-ray techniques as to the inability of existing angiographic methods to visualize the vessel walls, plaques and material (thrombus, blood, etc.) behind wall dissections. Accordingly, a method for simultaneously obtaining three-dimensional NMR angiograms and three-dimensional images of stationary tissue, in the same anatomical region, is highly desirably.